Anionic polymerization of functionalized styrene derivatives containing carbazole

ABSTRACT

Disclosed are functionalized styrene derivatives containing carbazole and their anionic polymerization. Styrene derivatives containing carbazole, and homopolymers or copolymers of the styrene derivatives can be synthesized by the anionic polymerization method. Thusly synthesized high molecular weight polymer containing carbazole has advantages of thermal stability, optical properties, and defined molecular weight and limited molecular weight distribution.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to functionalized styrenederivatives containing carbazole and their anionic polymerization. Morespecifically, the present invention relates to styrene derivativescontaining carbazole, and an improvement in the thermal stability,optical properties, and molecular weight and molecular weightdistribution of homopolymers or copolymers of the styrene derivatives,along with the anionic polymerization method. The term, opticalproperties, as used herein include photoluminescence andphotoconductivity.

[0003] 2. Description of the Prior Art

[0004] Carbazole-containing materials have been widely used asphotoconductive, refractive and non-linear optical materials, and havebeen recently reported to be useful as media of photoluminescencematerials [(1) Y. Zhang, T. Wada, and H. Sasabe, Chem. Commun., 1996,621. (2) Y. Zhang, T. Wada, and H. Sasabe, Macromol. Chem. Phys., 1996,197, 667. (3) K. Tamura, A. B. Padias, H. K. Hall Jr., and N.Peyghambarian, Appl. Phys. Lett., 1992, 60, 1803.].

[0005] In addition, it is reported that carbazole-containing materials,together with associated metals, have been used as polymers forelectrophotoluminescence [A. Ribou, T. Wada, and H. Sasabe, InorganicaChemica Acta, 1999, 288, 134].

[0006] The photorefractive polymers must preferably have low glasstransition temperature, while the electrophotoluminescent polymers mustpreferably have high glass transition temperature in consideration ofthermal stability. Therefore, if glass transition temperature can becontrolled by the molecular weight of the polymers, the polymers can beused for various applications.

[0007] Since anionic polymerization of styrene has been found,researches have been actively carried out. Recently, anionicpolymerization techniques have been developed, so styrene can beprepared in large scale through such polymerization at plants.

[0008] However, in the case of styrene with functional groups,undesirable side-reactions occur during the polymerization. In thisregard, it is reported that, in styrene derivatives with functionalelectron donating groups to the para-position, side-reactions are causedso that molecular weight and molecular weight distribution of thepolymer cannot be controlled [T. Ishizone, T. Utake, Y. Ishino, A.Hirao, and S. Nakahama, Macromolecules, 1987, 30, 6548]. Furthermore,when methylene group is introduced into styrene as a functional group,highly reactive chain ends of the polymer attack methylene group duringpolymerization, thus it is not easy to obtain well-controlled polymers.

[0009] Much efforts have been directed toward successfully synthesizingpolymers by introducing a functional group-protecting group to thepolymerization reaction, and then removing the protecting group afterthe polymerization [T. Ishizone, G. Uehara, A. Hirao, S. Nakahama, andK. Tsuda, Macromolecules, 1998, 31, 3764].

[0010] When monomer is in a liquid state, pure monomer can be obtainedby distillation or other processes, while monomer of solid state hassome impurities because distillation cannot be performed in a vacuum.Hence, such impurities reduce activity of starting materials, andconsequently molecular weight and molecular weight distribution of thepolymer cannot be easily controlled.

SUMMARY OF THE INVENTION

[0011] Accordingly, an object of the present invention for alleviatingthe problems as described above is to provide a polymer and a method forsynthesizing the same, in which a carbazole-containing solid styrenemonomer is used at lowered reaction temperature which restrainsside-reactions, so that a homopolymer with defined molecular weight andlimited molecular weight distribution is resulted, and such homopolymerand a carbazole-containing styrene derivative are block-copolymerizedwith other monomers, thereby obtaining a polymer with defined molecularweight.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The above and other objects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

[0013]FIG. 1 shows a reaction scheme of a mechanism for undesirableside-reactions during polymerization used in the present invention.

[0014]FIG. 2 shows a reaction scheme for synthesizing thecarbazole-containing monomer of the present invention.

[0015]FIG. 3 shows a reaction scheme of anionic polymerization used inthe present invention.

[0016]FIG. 4 shows a TGA curve of thermal properties of the synthesizedpolymer in the present invention.

[0017]FIG. 5 shows DSC curves of thermal properties of the synthesizedpolymer in the present invention.

[0018]FIG. 6 shows spectra of photoluminescence properties ofhomopolymer synthesized in the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0019] Based on the present invention, synthesized are a homopolymerwith controlled molecular weight and narrow molecular weightdistribution of the monomer,4-methylcarbazolyl styrene monomercontaining carbazole, and a controlled block copolymer of the monomerwith styrene, methylmethacylate (MMA) or 9-ethylcarbazollyl methacrylate(CzMA).

[0020] Carbazole was reacted with 1.5-fold excess of 4-vinylbenzylchloride in benzene/water using NaOH as a base, andbenzyltriethylammonium chloride as phase catalyst to afford4-(9-carbazolyl)methylstyrene (CMS) at 80° C. for 5 h. The reactionmixture was extracted with chloroform and the organic layer washed withwater, evaporated, and washed with hexane several times. The solid wasdissolved in and recrystallized from diethyl ether at −20° C. Yield:80%. The solid monomer was dried over P205 at 10-6 mmHg for 1 week andthen dissolved in anhydrous THF and stored at −30° C. in glass ampoulesunder high vacuum. This reaction scheme is schematically shown in FIG.2. The monomer is characterized by using 1H-NMR, 13C-NMR and FT-IR.Undesirable side-reaction of the monomer prepared is seen in FIG. 1.

[0021] From the monomer obtained above, poly(4-(9-carbazollylmethylstyrene)), being a homopolymer, is synthesized as follows.

[0022] Anionic polymerizations were carried out in THF under high-vacuumconditions (10-6 mmHg) for 5 min to 24 h in an all-glass apparatusequipped with break-seals in the usual manner. For thehomopolymerization of CMS, a THF solution of the CMS was added toK-Naph. solution in THF at −45 or −78° C. and allowed to react for 5 minto 24 h, and then terminated with methanol. The polymers wereprecipitated in large amount of methanol, dried, dissolved in benzene,and freeze-dried. The yield of polymer was determined from 1H-NMR data.

[0023] The synthesis of the block copolymers is carried out by thefollowing procedure.

[0024] Styrene was polymerized with K-Naph. in THF at −78° C. in allglass apparatus in vacuo. After 30 min, a portion of living polystyrenewas withdrawn to attached receiver to determine characteristic of thehomopolymer. The second monomer, CMS, in THF solution was added to theliving homopolystyryl solution in THF solution, polymerized for 24 h at−78° C., terminated with methanol, and precipitated in the large amountof methanol. Also, the reverse triblock copolymer between CMS andstyrene,PS-b-PCMS-b-PS(Polystyrene-Block-Carbazolylmethylstyrene-Block-Polystyrene),was synthesized by sequential addition of CMS and styrene.

[0025] A reaction scheme of high molecular weight polymer of the presentinvention according to the anionic polymerization method can be seen inFIG. 3.

[0026] A better understanding of the present invention may be obtainedin light of the following examples which are set forth to illustrate,but are not to be construed to limit the present invention.

EXAMPLES 1-9

[0027] Synthesis of Homopolymer of CMS at −45° C. and −78° C. TABLE 1CMS HOMOPOLYMER SYNTHESIZED AT −45° C. and −78° C. Conc. (mmol)Molecular MW K- Time Temp. Yield Weight (MW) Distribu- Run Naph CMS(min) (° C.) (%) Calcd obsd tion 1 0.099 1.715 10 −45 49.2 4,800 8.602.05 0 2 0.100 1.731 20 −45 54.8 5,400 9.90 2.09 0 3 0.102 1.700 30 −4564.1 6,100 10.7 2.04 00 4 0.099 1.667 120 −45 67.2 6,400 10.0 2.11 00 50.095 1.613 10 −78 91.0 8,700 9.60 1.67 0 6 0.097 1.686 20 −78 93.39,200 9.70 1.58 0 7 0.104 1.819 30 −78 97.3 9,700 9.50 1.65 8 0.0961.536 24h −78 98.0 8,900 8.80 1.55 0 9 0.094 1.766 10 −78 96.0 10,6009.30 1.28 0

[0028] CMS is soluble in a wide range of organic solvents such asDMF(N,N-dimethylformamide), DMSO (dimethylsulfoxide),THF(tetrahydrofuran) and so on. However, it is insoluble in mostnonpolar solvents such as hexane, benzene etc. The polymerization of CMSwas attempted with K-Naph. in THF at either −45 or −78° C. In each case,the reaction mixture always showed a deep red color during the course ofthe polymerization. The characteristic red color indicates the formationof styryl anion derived from CMS. The red color remained in THF evenafter 24 h, however, it immediately disappeared upon addition of a smallamount of methanol to quench the polymerization, indicating theexistence of the living ends.

[0029] Table 1 shows the homopolymerization results of CMS in THF at−45° C. under high vacuum condition. The yields of the polymer levels upafter 30 min. The MWD(Molecular Weight Distribution) of PCMS was broad,about 2.0, and SEC curve of PCMS has shoulder. Also, the observedmolecular weight is higher than the calculated value from [M]/[I]ratios.

[0030] In the anionic polymerization of (3-vinylphenyl)methyl methylsulfide, reported by Nakahama et al, gelled polymeric materials wereobtained during polymerization in THF at −78° C. due to the radicalcombination, induced by 1,6-elimination at the reactive chain end, toform a crosslinked network. Also, Nakahama et al. reported thepolymerization results of hexynylstyrene derivatives at highertemperature, 20 and 40° C. The SEC curve showed multimodal peaks due tothe proton abstraction after the completion of the polymerization.However, there is no crosslink reaction observed during and afterpolymerization of CMS. This means there is no radical forming reactionduring polymerization. Therefore, it may be due to the undesirable sidereaction such as the methylene proton abstraction by reactive chain endin THF at −45° C. The propagating chain end derived from PCMS isdeactivated at −45° C. Probably, the reason of this deactivation is theproton abstraction from the methylene group of the CMS, because theproton is known to be acidic.

[0031] Table 1 also shows the homopolymerization results of CMS in THFat −78° C. under high vacuum condition. The yields of the polymers inTHF at −78° C. rapidly increased in the initiation step. The yieldreached 91.0% within 10 min but slowly increased to 98.0% within 1 day.It may be due to the crystallization of the monomer at −78° C. duringthe polymerization, and slowly dissolved again in THF. Therefore, ittakes long time to get 100% yield. The observed molecular weight of thepolymer was in good agreement with the calculated molecular weight.However, the MWD is still broad even when polymerization was carried outat low temperature due to both the crystallization of the monomerleading to inhomogeneous solution during the polymerization and the sidereaction. Therefore, it is highly difficult to get narrow MWD even indilute solution. However, still unimodal peak was observed withoutshoulder. It appears that any possible side reactions mentioned inprevious could be eliminated or reduced at −78° C.

[0032] The thermal properties of the synthesized homopolymer wasmeasured by use of differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA) The results are shown in FIGS. 4 and 5. Byusing TGA, the decomposition temperature of the polymer was found to be416 C, at which weight loss of 5 wt % occurs, as best seen in FIG. 4.

[0033] The glass transition temperature was measured using DSC, and thetemperature was seen to change from 159 C to 173 C, depending on themolecular weight, as seen in FIG. 5. The prepared polymer has morethermally stable structure than polystyrene polymer, because polystyrenepolymer has a decomposition temperature of 304 C and a glass transitiontemperature of 100 C.

[0034] From Table 2, when the molecular weight is 3,000 or more, theglass transition temperature exceeds 150 C. When the molecular weight is10,000 or more, the temperature becomes constant at 173 C, though theglass transition temperature depends on the molecular weight. TABLE 2CHANGE OF GLASS TRANSITION TEMPERATURE OF HOMOPOLYMER ACCORDING TOMOLECULAR WEIGHT Molecular weight 3,200 8,600 9,100 9,600 12,000 15,000Glass Transition 159 169 171 171 173 173 Temp. (° C.)

[0035] CMS synthesized in the present invention has luminescentproperties, and is excited at a wavelength of 325 nm by use of He—Cdlaser, whereby the luminescence peak is seen at 350.5 nm and 365.5 nm,as can be shown in FIG. 6.

EXAMPLES 10-13

[0036] Synthesis of Copolymer of CMS and Styrene or Other Monomer TABLE3 PROPERTIES OF COPOLYMER SYNTHESIZED FROM CMS AND STYRENE OR OTHERMONOMERS Reaction Con. (mmol) MW K- Time Temp. Yield calc MW Run NaphCMS Styrene DPE MMA CzMA (min) (° C.) (%) d obsd Dis. 10 0.09 2.03 5.55120 −78 100 25.7 27.0 1.5 1 0 2 00 00 1 11 0.10 0.83 5.43 120 −78 10016.0 17.0 1.4 4 9 7 00 00 7 12 0.13 2.15 0.15 5.10 300 −78 98 17.5 20.01.4 0 3 3 6 00 00 8 13 0.11 2.15 0.12 2.12 300 −78 100 22.0 23.0 1.4 1 82 9 00 00 8

EXAMPLE 10 First Added Monomer-CMS, Second Added Monomer-Styrene EXAMPLE11 First Added Monomer-Styrene, Second Added Monomer-CMS

[0037] From the result of Table 3, it can be seen that, after CMS ishomopolymerized, useful as the second added monomer, styrene,methylmethacylate (MMA) or 9-ethylcarbazollyl methacylate (CzMA) isadded, thereby synthesizing a block copolymer. This means that thesecond monomer is added to reactive terminals of CMS to further performa polymerization. From the synthesis of the block copolymer of CMS andstyrene, it can be confirmed that the block copolymer is synthesizedregardless of addition order of CMS and styrene to the reaction.Accordingly, reactivity of CMS and styrene is assumed to be similar.Also, it is seen from the data of the block copolymers of CMS and MMA orCzMA that the reactivity of CMS is larger than that of MMA and CZMA.

[0038] In accordance with the method of the present invention, ahomopolymer and a block copolymer can be synthesized by use of a solidstyrene monomer containing carbazole.

[0039] The polymer of the present invention synthesized fromcarbazole-containing monomers with optical properties is advantageous interms of various optical properties, limited molecular weightdistribution, and improved thermal stability and solubility.Accordingly, the temperature is decreased on polymerization and thusside-reactions are minimized, so that the solid monomer can besynthesized according to the method of the present invention.

[0040] The present invention has been described in an illustrativemanner, and it is to be understood that the terminology used is intendedto be in the nature of description rather than of limitation. Manymodifications and variations of the present invention are possible inlight of the above teachings. Therefore, it is to be understood thatwithin the scope of the appended claims, the invention may be practicedotherwise than as specifically described.

What is claimed is:
 1. 4-mehylcarbazollylstyrene containing carbazole.
 2. A method for synthesizing homopolymer, poly(4-(9-carbazollylmethylstyrene)), by using 4-methylcarbazollyl styrene of claim 1 as monomer.
 3. The method as set forth in claim 2, wherein a reaction temperature is −78° C.
 4. The method as set forth in claim 2, wherein tetrahydrofuran is used as solvent.
 5. Poly(4-(9-carbazollylmethylstyrene)), homopolymer containing carbazole, prepared by the method of claim
 2. 6. Poly(4-(9-carbazollylmethylstyrene)) as set forth in claim 5, wherein a reaction temperature is −78° C.
 7. Poly(4-(9-carbazollylmethylstyrene)) as set forth in claim 5, wherein tetrahydrofuran is used as solvent.
 8. A method for synthesizing a block copolymer of 4-methylcarbazollylstyrene of claim 1 and styrene, MMA or CzMA.
 9. The method as set forth in claim 8, wherein a reaction temperature is −78° C.
 10. The method as set forth in claim 8, wherein tetrahydrofuran is used as solvent.
 11. A block copolymer prepared by the method of claim
 8. 